System of control.



R. E. FERRIS.

SYSTEM OF CONTROL.

APPLICATION FILED APE-4, 1914.

1,227,413. Patented May 22, 1917.

Graund WITNESSES: INVENTOR 1% r ATTORNEY UNITED STATES PATENT OFFICE.

BAIIPE E, rnnnrs, or SWISSVALE, PENNSYLVANIA, ASSIGNOR 'ro WESTINGHOUSEnmc'rmo AND mANUrAo'rUnINo oomrA'NY, A CORPORATION or PENNSYLVANIA.

SYSTEM OF CONTROL.

Specification of Letters Patent. Patented May 22, 1917.

' Application filed Apr114, 1914. Serial No. 829,427.

To all whom it may concern:

Be it known that I, RALPH E. Farms, a citizen of theUnited States, and aresident of Swissvale in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in Systems ofControl, of which the following is a specification.

My invention relates to systems of control for electric motors, and ithas special reference to means for supplying a suitably low, andapproximately constant, voltage to a receiving circuit, such, forexample, as the control or lighting circuit of an electric railwaytrain, from a plurality of supply circuits of materially differentvoltages.

One of the objectsof my invention is to provide an apparatus of themotorgeneratortype that is adapted to be operated from any one of aplurality of supply circuits of materially different voltages, whilemaintaining a substantially constant voltage delivered from thegenerator.

Another object of my invention is to provide, in a system of theabove-indicated character, means for maintaining a substantiallyconstant voltage in the receiving circuit throughout relatively wide andsudden changes in the load conditions on the electric motors.

Another object of my invention is to provide' an apparatus of thisgeneral class which shall be compact and durable in construction andflexible and reliable in opera tion.

In modern interurban direct-current rail way systems, it is often founddesirable and necessary, for various operating reasons, to supplyvarious portions of the transmission systems or supply circuits withvoltages of materially difi'erent values, for instance, 600 volts whenoperating in or near city properties, and 1200 volts when running on theinterurban portions ofthe lines. It appears probable that in the nearfuture even higher ing apparatus, such as is customarily emblower arepreferably driven continuously by the series-type motors, therebypreventing an excessive running speed thereof. The compressing apparatusis preferably automatically connected to the driving motors at intervalsthat are dependent upon the degree of air pressure in the system. Theload variations, thus intermittently imposed upon the motors, have theeffect of changing their speed and, consequently, the delivered voltageof the mechan cally associated generator, unless some suitablecounteracting means is provided. Accordingly, the system of the presentinvention comprises various means for varying the field excitation ofthe driving motors to maintain a substantially constant speed thereof orfor varying the fieldv excitation of the generator, thereby tending tosupply asubstantially constant voltage to the receiving circuit. Inaddition, a suitable" switching means is provided for properlyconnecting the motors to any one of the supply c1rcuits, as occasion mayrequire. For. example, if each motor armature winding is inherentlyadapted for operation at 600 volts, and if four such windings areemployed, then, by parallel, series-parallel and series-circuitarrangements of the windings, the apparatus may be readily operated at600, 1200 and 2400 volts, respectively, while maintaining substantiallyuniform operating characteristics of the generator.

In the accompanying drawing, Figure 1 is a plan View of an apparatusconstructed in accordance with my invention, Fig. 2 is a diagrammaticview of a control system embodying the apparatus shown in Fig. 1, andFigs. 3 and 4 are diagrammatic views of modifications of the controlsystem illustrated in Fig. 2.

Referring to Fig. 1 of the drawing, the apparatus here shown comprises aplurality of electric motors 1 and 2, preferably of the doublecommutator tytpe, severally provided with a plurality o armaturewindings, (not shown) that are severally connected to commutatorcylinders 3, 4, 5 and 6; a generator 7, of any suitable type, that ismechanically associatedwith the armatures of the motors 1 and 2 by meansof a suitable gear train 8, or inany other suitin my co-pendingapplication, Serial No.

809,635, filed December 31st, 1913.

Reference may now be had to Fig. 2 wherein the control system showncomprises a plurality of supply circuits, such as trolley conductors V,2V and 4V that are, provided with a common return conductor markedGround. The electric motors 1 and 2 are diagrammatically represented bythe commutator cylinders 3 to 6, inclusive, and .a plurality ofcorresponding subdivided series field windings 13. T e generator 7 isprovided with a variable'shunt field winding 14, and a receiving circuit15, such as the control and lighting circuits of an electric railwaysystem, is connected across the terminals of the generator. A suitableswitching device 16 is mechanically associated with the clutch 10 forsimultaneously short circuiting a portion of each the motor series fieldwindings 13, by means of. a plurality of magnet switches 13, theenergizing coils of which are adapted to be excited by a battery SB, fora purpose to be here inafter specified.

The volta es of the supply circuits 2V and 4V are pre erably multiplesof the, Volta e of the supply circuit V, as indicated by t e referencecharacters Switches 17 are provided. or connecting the driving motors tothe circuits V, 2V and 4V in series, series-parallel and series-circuitrelation, respectively, according to the relative positions of theswitches. For the sake of clearness, the circuits for connecting themotors in series relation across the supply circuit 4V are indicated inheavy solid lines, the control circuits-supplied from the circuit 2V areindicated in 'light lines and the control circuits connected to thesupply cir- Y cuit V are indicated in dotted-lines. The

operation maybe described as follows: Assuming that each of the motorarmature windings is inherently adapted for operation from a sup lycircuit of V volts, then, by suitable manlpulation of the switches 17,the armature windings maybe connected to any one of the three supplycircuits shown and, in any case, will operate atasubstan-j tiallyconstant speed. The speed and, consequently, the voltage of themechanically associated generator 7 will, therefore, remain ap lied tothem.-

substantially the same, irrespective of which supply circuit the motorsare operated from: When the fluid-compressing apparatus is not inoperation, a' certain relatively low motor current and motor speed willobtain; and, when the apparatus is connected to the motors by theactuation of the clutch 10, as more specifically set forth in myco-pending application, hereinbefore identified, a predeterminedincrease in load will be imposed upon the series motors, and the speedthereof will, consequently, tend to decrease. However, upon theactuation of the clutch 10, the switch 16 is closed to cause theshortcircuiting of a portion of each of the motor series field windings13, by reason of the energization of the coils of the magnet switches13", thereby weakening the field flux and causing the motors to increasetheir speed. By suitable design of the-field Windings 13, the speed andvoltage of the driven generator 7 may be maintained substantiallyconstant throughout the variations of load referred to. r

In Figs. 3 and 4, for the sake of clearness and simplicity, theseries-parallel switching means illustrated in connection. with themotors in Fig. 2 have been omitted; it will be understood, however, thatthe operation of the motors is the same as described in connection withFig. 2.

In Fig. 3 a series-type field winding 18 for the generator armature 7 isshown as connected in series relation with the motor series fieldwindings 19. By suitably designing and proportioning the field windings18 and 19 with respect to the magnetic circuits of the correspondingarmatures, or, in other words, by designing the motors and the generatorto have the same magnetization curve or magnetic saturation properties,the voltage delivered to the receiving circuit 15 by the generator maybe maintained substantially constant, inasmuch as a decrease of thespeed of all the machines by reason of an increased motor load, such asthe connection of the fluid-compressing apparatus, is substantiallycompensated for by the increased current traversing the generator fieldwinding 18, and vice versa, whereby the flux traversing the generatorarmature 7 varies practically inversely as the armature speed, and theresultant voltage remains substantially constant.

In Fig. 4, in addition to the circuits illustrated in Fig.3,- aseparatelyexcited fieldwinding circuit 20 for the driving motors isprovided and is connected across the termi nals of the generator 7. Itwill be understood that,by reason of the shunt characteristic thussupplied to the motors, a mechanical load for preventing anexcessivemotor s eed is unnecessary. The operation of t is system may be brieflydescribed as followsrUpon the connection of the fluid-compressingapparatus 9 to the driving motors, the tendency to decreasethe'motorspeed tends also to reduce the voltage of the generator. Conan increasein motorspeed, in accordance with well known PIHICIPlGSJ By a properdesign ofparts, the speed of the motors may thus be maintainedsubstantially constant, with the result that the voltage of thereceiving'circuit is also kept substantially the same.

I do not wish to be restricted to the specific structural details andcircuit connections herein set forth for illustrative purposes, butdesire that only such limitations shall be imposed as are indicated inthe appended claims.

I claim as my invention: I

1. A control system comprising a supply circuit, a plurality ofmechanically associated dynamo-electric machines fed therefrom, meansfor varying {the load upon said machines by a'; iedetermined amount,another dynamofe ectric machine driven by said first machines, and meansfor maintaining. the voltage of said last machine substantiallyconstant, asthe said load varies.

\ 2. A control system, comprising a supply circuit, a plurality ofmechanically associated driving dynamo-electric machines fed therefrom,a driven apparatus adapted to vary the load upon said machines b apredetermined amount, a generating ynamoelectric machine driven by saidfirst machlnes, and means dependent upon the load variations for varyingthe electrical conditions in said generating machine to maintain thevoltage thereof substantially constant,

as the said load varies.

3. A. control system comprising a supply circuit, a plurality ofmechanically associated electrlc motors connected in series-relationacross said circuit, a fluid compressing apparatus adapted to bemechanically connected to said motors, a generator driven by saidmotors, and switching means dependent upon the mechanical connection anddisconnection of said apparatus for varying the exciting field currentof said enerator to maintain the voltage thereof substantially constant,as the load varies.

4. In a control system, the combination with a supply circuitofrelatively high voltage, of a plurality of mechanically associateddynamo-electric machines fed therefrom, means for varying the load uponsaid machines by a predetermined amount, another dynamo-electric machinedriven by said first machines, a receiving circuit of relatively lowvoltage connected to said last machine, and means for maintaining the avoltage of said receiving circuit substantially constant, as the saidload varies.

5. In a control system, the combination with a supply circuit ofrelatively high voltage, of a plurality of mechanically associ= ateddriving,dynamo-electric machines fed therefrom, a driven apparatusadapted to vary the load upon said machines by a pre- 7 determinedamount, a generating dynamoelectric machine driven by said firstmachines, a receiving circuit of, relatively low voltage connectedacross said last machine, and means dependent upon the load varia 7tions for varying the electrical conditions in said generating machineto maintain the voltage thereof substantially constant, as the said loadvaries.

6. In a control system, the combination with a supply circuit ofrelatively high voltage, of a plurality of mechanically associatedelectric motors connected in series relation across said circuit, afluid-compressing apparatus adapted to be mechanically 35 connected tosaid motors, a generator driven by said motors, a receiving circuit ofrelatively low voltage connected across said generator, and switchingmeans dependent upon the mechanical connection and disconnection of saidapparatus for varying the exciting field current of said generator tomaintain the voltage thereof substantially constant, as the load varies.

7. A control system comprising a plurality of supply circuits ofmaterially different voltages, a plurality of mechanically associateddriving dynamo-electric machines, means for connecting'said machines inproper relative circuit relation to any of 1 said supply circuits, adriven apparatus adapted to vary the load upon said machines by apredetermined amount, a generating dynamo-electric machine driven bysaid first machines, and means dependent 7 upon the load variations forvarying the electrical conditions in said generating machine to maintainthe voltage thereoi substantially constant, as the said load varies.

8, A control system comprising a plu- 113 rality of supply circuits ofmateriallydifferent voltages, the higher voltages being substantialmultiples of the lowest voltage,

a plurality of mechanically associated electric motors severallyinherently adapted for 115 operation from said lowest voltage, means forconnecting said machines in parallel circuit relation across the supplycircuit of lowest voltage, in series-parallel circuit relation' acrossthe supply circuit of next 1 higher voltage, and in series-circuitrelation across the circuit of highest voltage, a fiuid compressingapparatus adapted to be mechanically connected to said motors, agenerator driven by said motors, and switching means dependent upon themechanical connection and disconnection of said apparatus for varyingthe exciting field current,

of said generator to maintain the voltage thereof substantiallyconstant, as the load varies. v

9. A control system comprising -a supply circuit, aplur'ality ofmechanically associated driving dynamo-electric machines severallyhaving series field windings divided into sections, a driven apparatusadapted to vary the load upon said machines by a predetermined amount,and a generating dynamo-electric machine driven by said drivingmachines, of means for varying the active portions of said drivingdynamo-electric machine field windings in accordance with the load onsaid driving machines.

10. In a control system, the combination with a supply circuit, aplurality of mechanically associated electric motors severally havingseries field windings divided into 'sections, a fluid-compressingapparatus adapted to be -mechanically connected to said motors, agenerator driven by said motors, and a receiving circuit of relativelylow voltage connected across said generator, of means for varying theactive portions of said motor field windings in accordance with the loadon said motors to maintain the speed thereof substantially constant.

11. A control system comprising a supply circuit, a plurality ofmechanically associated electric motors fed therefrom, means for varyingthe load upon said machines by a predetermined amount, a generatingmachine driven by said motors, and means dependent upon the loadvariations for varying the field excitation of said motors to maintainsubstantially constant speed thereof, whereby the generating machinevoltage. remains substantially constant, as the load varies.

12. A control system comprising a supply circuit, a plurality ofmechanically associated electric motors fed therefrom, afluid-compressing apparatus adapted to be mechanically connected to said'motors, a generator driven by said motors, and switching meansdependent upon the mechanical connection and disconnection of said apnratus for varying the active portions 0 the motor field windings tomaintain substantially constant speed of the motors, whereby thegenerating machine voltage remain sub- ,7

RALPn FERRIS. -Witnesses: I

CERWIN R. CASE, B. B. HINES.

